1. Technical Field
The present invention relates to a transfusing device and a liquid supply tube and, in particular, to a structure suitable for a transfusing device for injecting a liquid medicine into the body of a patient and to a structure suitable for a liquid supply tube, which is a constituent part of a transfusing device.
2. Background Art
In a hospital or the like, a liquid medicine is injected into the body of a patient usually by drip transfusion, in which a plastic transfusing tube is connected to a liquid medicine sack, which is suspended from above, and a needle is attached to the forward end of the transfusing tube and inserted into a blood vessel of the patient or the like. To accurately control the amount of liquid medicine or to enhance the safety of the operation, various types of transfusing device constructed so as to be capable of forcibly sending the liquid medicine into the body of the patient may be adopted.
In one type of such transfusing device, a peristaltic transfusing pump may be employed in which the liquid medicine in a flexible liquid supply tube is conveyed by squeezing the liquid supply tube. Two types of peristaltic transfusing pump are employed: one is a rotary type transfusing pump in which a flexible liquid supply tube is bent into a semi-circular shape and in which the bent portion of the liquid supply tube is squeezed from inside to conveyed liquid medicine by a roller mounted to the forward end of a rotatable arm provided on the inner side of the bent portion of the liquid supply tube; and the other is a finger type transfusing pump in which a plurality of fingers (pressurizing members) are sequentially pressed against the outer surface of the liquid supply tube in the direction in which the liquid medicine in the liquid supply tube is to be conveyed to thereby convey the liquid medicine.
The rotary type transfusing pump is advantageous in that it has a relatively simple structure. However, it is relatively difficult to accurately control the minute amount of liquid medicine to be conveyed. Further, it does not easily allow the size of the conveying section to be reduced.
A typical example of the finger type transfusing pump is disclosed in Japanese Patent Publication No. 61-55393. In the transfusing pump of the above example, a finger is engaged with each of a plurality of cam plates mounted to a rotation shaft, and the fingers are caused to move toward and away from the liquid supply tube by rotating operation of the cam plates when the rotation shaft rotates. This peristaltic transfusing pump using fingers is advantageous in that the injection pressure for the liquid medicine can be made high and that the minute amount of liquid medicine can be controlled with high accuracy. However, since it is necessary to drive a large number of fingers with high accuracy, the structure of the pump is rather complicated, making it difficult to reduce the production cost. Further, it is difficult to achieve a reduction in size.
A balloon type transfusing device provides a function equivalent to that of the above transfusing device. In the balloon type transfusing device, liquid medicine is put in the balloon, which is formed of synthetic rubber or the like, in advance, and the liquid medicine is pushed forward by contraction force of the balloon. This transfusing device is advantageous in that it has a very simple structure and can be produced at low cost. However, in a transfusing device using a balloon, the discharge pressure of the liquid medicine varies depending upon the amount of liquid medicine left in the balloon, so that the speed at which the liquid medicine is supplied also varies. More specifically, the discharge pressure is gradually reduced from the initial pressure as the transfusion time elapses, and the amount of liquid medicine supplied also diminishes gradually. In this way, the supply pressure for the liquid medicine and its amount supplied vary. Further, it is difficult to control the speed at which the liquid medicine is supplied.
In performing medical treatment, it is sometimes necessary to give a minute amount of liquid medicine over a long period of time to mitigate the strain on the patient. To make it possible to give liquid medicine over a long period of time, development of a portable transfusing device is to be expected. To realize a portable transfusing device, a reduction in the size and weight of the device is indispensable. Conventionally, there has been proposed no transfusing device structure which is small and light enough to provide a satisfactory portability. Further, it is not yet technically possible to administer a minute amount of liquid medicine into the body of the patient with high accuracy.